Acetabular cup prosthesis alignment system and method

ABSTRACT

Technologies for aligning an acetabular prosthetic component in a patient&#39;s surgically prepared acetabulum include a reference sensor module securable to the patient&#39;s bony anatomy, an inserter sensor module securable to an acetabular prosthetic component inserter, and a display module. Each sensor module generates sensor data indicative of the orientation of the sensor module and/or structures to which the sensor module is coupled. The display module receives the sensor data from the sensor modules, determines the orientation of the acetabular prosthetic component relative to the patient&#39;s bony anatomy, and displays indicia of the determined orientation on a display.

This is a continuation application that claims priority to U.S. patentapplication Ser. No. 15/451,604, which was filed on Mar. 7, 2017 andclaims priority under 35 U.S.C. § 121 to U.S. patent application Ser.No. 13/834,993, now U.S. Pat. No. 9,585,768, which was filed on Mar. 15,2013, each of which is expressly incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to an implantable orthopaedicprosthesis, and more particularly to an implantable acetabularprosthesis and systems and methods of aligning acetabular prosthesesduring implantation.

BACKGROUND

Joint arthroplasty is a well-known surgical procedure by which adiseased and/or damaged natural joint is replaced by a prosthetic joint.For example, in a hip arthroplasty surgical procedure, a patient'snatural hip ball and socket joint is partially or totally replaced by aprosthetic hip joint. A typical prosthetic hip joint includes anacetabular prosthetic component and a femoral head prosthetic component.An acetabular prosthetic component generally includes an outer shellconfigured to engage the acetabulum of the patient and an inner bearingor liner coupled to the shell and configured to engage the femoral head.The femoral head prosthetic component and inner liner of the acetabularcomponent form a ball and socket joint that approximates the natural hipjoint.

To facilitate the replacement of the natural joint with a prosthetic hipjoint, orthopaedic surgeons may use a variety of orthopaedic surgicalinstruments such as, for example, reamers, drill guides, drills,positioners, and/or other surgical instruments. The acetabular componentis typically inserted into the patient's acetabulum using an acetabularprosthetic component inserter. Poor alignment of the acetabularprosthetic component relative to the patient's bony anatomy can resultin component loosening and/or dislocation over time and use of theprosthetic hip joint.

SUMMARY

According to one aspect, a system for aligning an acetabular prostheticcomponent in a patient's surgically prepared acetabulum includes areference sensor module securable to the patient's bony anatomy, aninserter sensor module securable to an acetabular prosthetic componentinserter, and a display module separate from the reference sensor moduleand the inserter sensor module. The reference sensor module includes (i)a first orientation sensor configured to generate first sensor dataindicative of the orientation of the patient's bony anatomy inthree-dimensions and (ii) a first communication circuit to transmit thefirst sensor data. The inserter sensor module includes (i) a secondorientation sensor configured to generate second sensor data indicativeof the orientation of the acetabular prosthetic component inserter inthree-dimensions, (ii) a second communication circuit to transmit thefirst sensor data, and (iii) an alignment indicator. The display moduleincludes (i) a display, (ii) a third communication circuit configured toreceive the first sensor data and the second sensor data, and (iii) aprocessing circuit to determine an orientation of an acetabularprosthetic component coupled to the acetabular prosthetic componentinserter relative to the patient's bony anatomy based on the firstsensor data and the second sensor data, display indicia of thedetermined orientation of the acetabular prosthetic component on thedisplay, and communicate with the inserter sensor module to activate thealignment indicator in response to the determined orientation beingwithin threshold amount of a reference orientation.

In some embodiments, the first orientation sensor may include a firstthree-axis gyroscope and a first three-axis accelerometer. Additionallyor alternatively, the second orientation sensor may include a secondthree-axis gyroscope and a second three-axis accelerometer. In someembodiments, each of the reference sensor module and the inserter sensormodule may include a power button selectable to turn on thecorresponding sensor module. In such embodiments, each of the referencesensor module and the inserter sensor module may be incapable of beingturned off by selection of the power button after the correspondingsensor module has been turned on.

In some embodiments, the alignment indicator may include a firstalignment indicator and a second alignment indicator. In suchembodiments, the processing circuit of the display module may beconfigured to (i) communicate with the inserter sensor module toactivate the first alignment indicator in response to the determinedorientation being within a first threshold amount of the referenceorientation and (ii) communicate with the inserter sensor module toactivate the second alignment indicator in response to the determinedorientation being within a second threshold amount of the referenceorientation that is less than the first threshold amount. Additionally,in some embodiments, the second alignment indicator may be bounded bythe first alignment indicator.

Additionally, in some embodiments, the processing circuit of the displaymodule may be configured to determine an inclination angle and ananteversion angle of the acetabular prosthetic component relative to thepatient's bony anatomy and display the inclination angle and theanteversion angle on the display. Additionally or alternatively, theprocessing circuit of the display module may be configured to display agraphical representation of the acetabular prosthetic component inserteron the display in a position based on the determined inclination angleand anteversion angle.

In some embodiments, the processing circuit of the display module may beconfigured to determine a coordinate system conversion factor to convertthe first sensor data from a coordinate system of the inserter sensormodule to a patient coordinate system of the patient's bony anatomy anddetermine the orientation of the acetabular prosthetic componentinserter relative to the patient's bony anatomy using the coordinatesystem conversion factor. Additionally, in some embodiments, thereference sensor module may include a housing having a first keyedstructure and the inserter sensor module includes a housing having asecond keyed structure. The first keyed structure and the second keyedstructure may be keyed to each other such that the reference sensormodule and the inserter sensor module can be coupled to each other in asingle orientation in which the first keyed structure and the secondkeyed structure are mated. For example, in some embodiments, the firstkeyed structure may be embodied as a raised platform extending upwardlyfrom a top surface of the housing of the reference sensor module and thesecond keyed structure may be embodied as a recess defined in a topsurface of the housing of the inserter sensor module, wherein the raisedplatform is received in the recess when the reference sensor module andthe inserter sensor module are coupled to each other in the singleorientation.

Additionally, in some embodiments, the system may include an alignmentframe. The alignment frame may include a frame body, a plurality ofcontact feet, and a cradle. In some embodiments, the contact feet may bemovable relative to the frame body. Additionally or alternatively, thecradle may be sized to receive the inserter sensor module.

According to another aspect, a method for aligning an acetabularprosthetic component in a patient's surgically-prepared acetabulumincludes securing a reference sensor module to the patient's bonyanatomy, securing an inserter sensor module to an acetabular prostheticcomponent inserter, generating, with the reference sensor module, firstsensor data indicative of the orientation of the patient's bony anatomyin three-dimensions, generating, with the inserter sensor module, secondsensor data indicative of the orientation of the acetabular prostheticcomponent inserter in three-dimensions, receiving, with a displaymodule, the first sensor data and the second sensor data, determining,with the display module, an orientation of an acetabular prostheticcomponent coupled to the acetabular prosthetic component inserterrelative to the patient's bony anatomy based on the first sensor dataand the second sensor data, displaying, on the display module, indiciaof the determined orientation of the acetabular prosthetic component ona display of the display module, and transmitting a control signal fromthe display module to the inserter sensor module to activate analignment indicator of the inserter sensor module in response to thedetermined orientation being within a threshold amount of a referenceorientation.

In some embodiments, securing the reference sensor module to thepatient's bony anatomy may include attaching the reference sensor moduleto a mounting frame and securing the mounting frame to the patient'sbony anatomy. Additionally, in some embodiments, the method may alsoinclude initializing the reference sensor module and the inserter sensormodule to compensate for bias offset of the corresponding generatedsensor data. For example, initializing the reference sensor module andthe inserter sensor module may include placing each of the referencesensor module and the inserter sensor module in a stationary positionrelative to each other. In some embodiments, placing each of thereference sensor module and the inserter sensor module in a stationaryposition relative to each other may include mating a keyed feature of ahousing of the reference sensor module with a corresponding keyedfeature of a housing of the inserter sensor module. Additionally oralternatively, initializing the reference sensor module and the insertersensor module may include transmitting identification data from each thereference sensor module and the inserter sensor module to the displaymodule and displaying the identification data on the display of thedisplay module.

In some embodiments, the method may also include registering theinserter sensor module to a patient coordinate system of the patient'sbony anatomy. For example, registering the inserter sensor module to thepatient coordinate system may include aligning the inserter sensormodule with a spine of the patient and aligning the inserter sensormodule with an anatomical axis of the patient defined by the anteriorsuperior iliac spine points of the patient's bony anatomy. In suchembodiments, the method may also include generating, with the insertersensor module, first alignment data indicative of the currentorientation of the inserter sensor module while aligned with the spineof the patient, generating, with the inserter sensor module, secondalignment data indicative of the current orientation of the insertersensor module while aligned with the anatomical axis of the patient, andgenerating a coordinate system conversion factor based on the first andsecond alignment data to convert sensor data generated by the insertersensor module from a coordinate system of the inserter sensor module toa patient coordinate system of the patient's bony anatomy. For example,determining the orientation of the acetabular prosthetic component mayinclude determining the orientation of the acetabular prostheticrelative to the patient's bony anatomy based on the first sensor dataand the coordinate system conversion factor.

In some embodiments, registering the inserter sensor module to thepatient coordinate system may include placing an alignment frame on thepatient in a position such that a first contact foot of the alignmentframe confronts a first anterior superior iliac spine point of thepatient, a second contact foot of the alignment frame confronts a secondanterior superior iliac spine point of the patient, and a third contactfoot of the alignment frame confronts a pubic symphysis of the patient.In such embodiments, the method may further include coupling theinserter module to the alignment frame.

Additionally, in some embodiments, determining the orientation of theacetabular prosthetic component may include determining an inclinationangle and an anteversion angle of the acetabular prosthetic relative tothe patient's bony anatomy. Additionally or alternatively, displayingindicia of the determined orientation of the acetabular prostheticcomponent may include displaying the inclination angle and theanteversion angle on the display of the display module. For example,displaying indicia of the determined orientation of the acetabularprosthetic component may include displaying a graphical representationof the acetabular prosthetic component inserter on the display in aposition based on the determined inclination angle and anteversionangle.

According to a further aspect, a system for aligning an acetabularprosthetic component in a patient's surgically prepared acetabulum mayinclude a reference sensor module securable to the patient's bonyanatomy and an inserter sensor module securable to an acetabularprosthetic component inserter. The reference sensor module may include(i) a housing having a first keyed structure, a (ii) a first orientationsensor positioned in the housing and configured to generate first sensordata indicative of the orientation of the patient's bony anatomy inthree-dimensions, and (iii) a first communication circuit to transmitthe first sensor data. The inserter sensor module may include (i) ahousing having a second keyed structure (ii) a second orientation sensorconfigured to generate second sensor data indicative of the orientationof the acetabular prosthetic component inserter in three-dimensions,(ii) a second communication circuit to transmit the first sensor data,and (iii) a housing having (iii) an alignment indicator. The first keyedstructure and the second keyed structure may be keyed to each other suchthat the reference sensor module and the inserter sensor module can becoupled to each other in a single orientation in which the first keyedstructure and the second keyed structure are mated.

In some embodiments, the first keyed structure may be embodied as araised platform extending upwardly from a top surface of the housing ofthe reference sensor module. Additionally, the second keyed structuremay be embodied as a recess defined in a top surface of the housing ofthe inserter sensor module, wherein the raised platform is received inthe recess when the reference sensor module and the inserter sensormodule are coupled to each other in the single orientation.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description particularly refers to the following figures,in which:

FIG. 1 is a simplified diagram of an system for aligning an acetabularprosthetic component in a patient's surgically prepared acetabulum;

FIG. 2 is a front elevation view of a reference sensor module and aninserter sensor module of the system of FIG. 1;

FIG. 3 is a top perspective view of the reference sensor module and theinserter sensor module of FIG. 2;

FIG. 4 is a bottom plan view of the reference sensor module and theinserter sensor module of FIG. 2;

FIG. 5 is a simplified block diagram of a circuit of the referencesensor module and the inserter sensor module of FIG. 2;

FIG. 6 is a simplified top plan view of a display module of the systemof FIG. 1;

FIG. 7 is a simplified block diagram of a circuit of the display moduleof FIG. 6;

FIGS. 8A-8B are a simplified flow diagram of a method for aligning anacetabular prosthetic component in a patient's surgically preparedacetabulum;

FIG. 9 is a simplified flow diagram of a method for initializing thereference sensor module and the inserter sensor module of FIG. 2;

FIG. 10 is a simplified flow diagram of a method for registering theinserter sensor module of the system of FIG. 1 to a patient coordinatesystem of the patient's bony anatomy;

FIGS. 11A-11B are a simplified flow diagram of a method for determininga coordinate system conversion factor to convert from a coordinatesystem of the inserter sensor module to the patient coordinate system ofthe patient's bony anatomy;

FIG. 12 is a simplified illustration of one initialization process ofthe reference sensor module and the inserter sensor module of the systemof FIG. 1;

FIG. 13 is a simplified illustration of the reference sensor module andthe inserter sensor module of the system coupled to each other usingkeyed features of the housings of the sensor modules;

FIG. 14 is a simplified illustration of the reference sensor module ofthe system of FIG. 1 secured to a bone mounting bracket;

FIG. 15 is a simplified illustration of the reference sensor module ofthe system of FIG. 1 secured to a patient's bony anatomy using themounting bracket of FIG. 14;

FIG. 16 is a simplified illustration of a coordinate system of thesensor modules of the system of FIG. 1;

FIG. 17 is a simplified illustration of a patient coordinate system ofthe patient's bony anatomy;

FIG. 18 is a simplified illustration of the inserter sensor module ofthe system of FIG. 1 aligned with the spine of the patient;

FIG. 19 is a simplified illustration of the inserter sensor module ofthe system of FIG. 1 aligned with an anatomical axis of the patientdefined by the anterior superior iliac spine points of the patient'sbony anatomy;

FIGS. 20-25 are illustration of various equations used to convert fromthe sensor coordinate system of FIG. 16 to the patient coordinate systemof FIG. 17; and

FIG. 26 is a simplified illustration of an embodiment of an alignmentframe that may be used to register the inserter senor module of FIG. 1with a patient coordinate system.

DETAILED DESCRIPTION OF THE DRAWINGS

While the concepts of the present disclosure are susceptible to variousmodifications and alternative forms, specific embodiments thereof havebeen shown by way of example in the drawings and will be describedherein in detail. It should be understood, however, that there is nointent to limit the concepts of the present disclosure to the particularforms disclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives consistent with the presentdisclosure and the appended claims.

References in the specification to “one embodiment,” “an embodiment,”“an illustrative embodiment,” etc., indicate that the embodimentdescribed may include a particular feature, structure, orcharacteristic, but every embodiment may or may not necessarily includethat particular feature, structure, or characteristic. Moreover, suchphrases are not necessarily referring to the same embodiment. Further,when a particular feature, structure, or characteristic is described inconnection with an embodiment, it is submitted that it is within theknowledge of one skilled in the art to effect such feature, structure,or characteristic in connection with other embodiments whether or notexplicitly described.

In the drawings, some structural or method features may be shown inspecific arrangements and/or orderings. However, it should beappreciated that such specific arrangements and/or orderings may not berequired. Rather, in some embodiments, such features may be arranged ina different manner and/or order than shown in the illustrative figures.Additionally, the inclusion of a structural or method feature in aparticular figure is not meant to imply that such feature is required inall embodiments and, in some embodiments, may not be included or may becombined with other features.

Terms representing anatomical references, such as anterior, posterior,medial, lateral, superior, inferior, etcetera, may be used throughoutthis disclosure in reference to both the orthopaedic implants describedherein and a patient's natural anatomy. Such terms have well-understoodmeanings in both the study of anatomy and the field of orthopaedics. Useof such anatomical reference terms in the specification and claims isintended to be consistent with their well-understood meanings unlessnoted otherwise.

Referring now to FIG. 1, a system 100 for aligning an acetabularprosthetic component 160 in a patient's surgically prepared acetabulumincludes a reference sensor module 102, an inserter sensor module 104,and a hand-held display module 106. In use, the reference sensor module102 is secured to the bony anatomy of the patient using a mountingbracket 110 and generates sensor data indicative of the orientation ofthe reference sensor module 102, and thereby the patient's bony anatomy,in three dimensions (i.e., rotation about each coordinate axis x, y, andz). Similarly, the inserter sensor module 104 is attached to anacetabular prosthetic component inserter 130 and generates sensor dataindicative of the orientation of the inserter sensor module 104, andthereby the acetabular prosthetic component inserter 130, in threedimensions. Each of the sensor modules 102, 104 transmit the generatedsensor data to the display module 106. The display module 106 determinesan orientation of the acetabular prosthetic component 160, which issecured to a distal end 132 of the acetabular prosthetic componentinserter 130, relative to the patient's bony anatomy as discussed inmore detail below.

As shown in FIGS. 2-4, each of the sensor modules 102, 104 includes acorresponding housing 202, 204 having a generally rectangular shape.Illustratively, each housing 202, 204 is embodied as a multi-piecehousing. However, housings having other shapes and configurations may beused in other embodiments.

The housing 202 of the reference sensor module 102 includes a topsurface 210, a bottom surface 212, a front panel 214, side surfaces 216,218, and a rear surface 220. The reference sensor module 102 alsoincludes a power button 230 defined on the front panel 214. The powerbutton 230 is selectable to turn on the reference sensor module 102.However, in some embodiments, the reference sensor module 102 may not beturned off after the sensor module 102 has been successfully turned on.That is, re-selection of the power button 230 does not turn off thereference sensor module 102. Rather, the reference sensor module 102will remain on until the power source (e.g., internal batteries) of thereference sensor module 102 is depleted as discussed in more detailbelow. In some embodiments, the power button 230 is backlit when thereference sensor module 102 is turned on to provide a visual indicationthat the reference sensor module 102 is powered on.

As shown in FIG. 3, the housing 202 of the reference sensor module 102also includes a keyed structure 240 defined on the top surface 210. Inthe illustrative embodiment, the keyed structure 240 is keyed to acorresponding keyed structure 280 of the inserter sensor module 104. Asdiscussed in more detail below, the keyed structures 240, 280 facilitatethe coupling together of the reference sensor module 102 and theinserter sensor module 104. Due to the keyed configuration of the keyedstructures 240, 280, the sensor modules 102, 104 can be coupled togetherin only a single orientation relative to each other in which the keyedstructures 240, 280 are mated together. In the illustrative embodiment,the keyed structure 240 is embodied as a raised platform 242 thatextends upwardly from the top surface 210. The raised platform 242 has asubstantially “Y”-shaped top profile and is arranged such that the widthof the raised platform 242 is greater toward the front panel 214 andnarrower toward the rear surface 220. Of course, in other embodiments,other configurations of the keyed structure 240 that enable coupling ofthe sensor modules 102, 104 in a single orientation in which the keyedstructures 240, 280 are mated may be used. For example, in someembodiments, the keyed structure 240 may be embodied as, or otherwiseinclude, a recess, additional raised platforms, and/or other structures.

The reference sensor module 102 also includes a mount 244 as shown inFIG. 4. The mount 244 facilitates attachment to the mounting bracket110. Illustratively, the mount 244 includes a mounting tab 246 andseveral alignment tabs 248. Of course, the mount 244 may have other oradditional structures and/or features in other embodiments to facilitatethe securement of the reference sensor module 102 to the mountingbracket 110. Regardless of the specific configuration, the referencesensor module 102 may be attached to a sensor mount base 112 of themounting bracket 110 using the mount 244. For example, in theillustrative embodiment, the mounting tab 246 is received in acorresponding aperture of the sensor mount base 112 and the alignmenttabs 248 clip to the side of the sensor mount base 112 to secure thereference sensor module 102 to the mounting bracket 110. As shown inFIG. 1, the mounting bracket 110 also includes an elongated rod 114extending from the sensor mount base 112 to a bone mount base 116. Thebone mount base 116 is configured to facilitate attachment of themounting bracket 110 to the bony anatomy of the patient and may includeone or more mounting aperture 118 configured to receive correspondingsecuring devices 120, such as bone screws or the like, to secure themounting bracket 110 to the patient's bony anatomy.

The inserter sensor module 104 is similar to the reference sensor module102. The housing 204 of the inserter sensor module 104 includes a topsurface 250, a bottom surface 252, a front panel 254, side surfaces 256,258, and a rear surface 260. The inserter sensor module 104 alsoincludes a power button 270 and an alignment indicator 272 defined onthe front panel 254. Similar to the power button 230 of the referencesensor module 102, the power button 270 is selectable to turn on theinserter sensor module 104 but not to subsequently turn off the insertersensor module 104. That is, as discussed above with regard to thereference sensor module 102, re-selection of the power button 270 doesnot turn off the inserter sensor module 104 in some embodiments. Rather,the inserter sensor module 104 will remain on until the power source(e.g., internal batteries) of the inserter sensor module 104 is depletedas discussed in more detail below. Similar to the reference sensormodule 102, the power button 270 of the inserter sensor module 104 maybe backlit when the inserter sensor module 104 is powered on to providea visual indication that the inserter sensor module 104 is on.

As discussed in more detail below, the alignment indicator 272 providesa visual feedback to the orthopedic surgeon whether the currentalignment of the acetabular prosthetic component 160 is within areference threshold of a target alignment. In the illustrativeembodiment, the alignment indicator 272 includes a first thresholdalignment indicator 274 and a second threshold alignment indicator 276.The first threshold alignment indicator 274 is embodied as a circularvisual indicator, such as a circular light, circular array of lightemitting diode, circular light filter, or the like. The first thresholdalignment indicator 274 bounds the second threshold alignment indicator276, which is embodied as a single visual indicator, such as a singlelight, light emitting diode, or the like. In use, the first thresholdalignment indicator 274 is illuminated in response to the alignment ofthe acetabular prosthetic component 160 being within a first thresholdof the reference alignment and the second threshold alignment indicator276 is illuminated in response to the alignment of the acetabularprosthetic component 160 being within a second threshold of thereference alignment that is less than first threshold. That is, when thesecond threshold alignment indicator 276 is illuminated, the alignmentof the acetabular prosthetic component 160 is closer to the referencealignment than when only the first threshold alignment indicator 274. Ofcourse, in other embodiments, the alignment indicator 272 may includeother or additional indicators.

As shown in FIG. 3, the housing 204 of the inserter sensor module 104includes a keyed structure 280 defined on the top surface 250. Asdiscussed above, the keyed structure 280 is keyed to the correspondingkeyed structure 240 of the reference sensor module 102. In theillustrative embodiment, the keyed structure 280 is embodied as a recess282 defined in the top surface 250 of the housing 204. Illustratively,the recess 282 has a shape corresponding to the shape of the raisedplatform 242 of the reference sensor module 102 such that the raisedplatform 242 may be received in the recess 282 when the sensor modules102, 104 are coupled to together as discussed below. In the illustrativeembodiment, the recess 282 has a substantially “Y”-shaped top profileand is arranged such that the width of the recess 282 is greater towardthe front panel 254 and more narrow toward the rear surface 260. Ofcourse, in other embodiments, other configurations of the keyedstructure 280 that enable coupling of the sensor modules 102, 104 in asingle orientation in which the keyed structures 240, 280 are mated maybe used. For example, in some embodiments, the keyed structure 240 maybe embodied as, or otherwise include, a raised platform, additionalrecesses, and/or other structures.

Similar to the reference sensor module 102, the inserter sensor module104 also includes a mount 290 as shown in FIG. 4. The mount 290facilitates attachment of the inserter sensor module to the acetabularprosthetic component inserter 130. The mount 290 is similar to the mount244 of the reference sensor module 102 and includes a mounting tab 292and several alignment tabs 294. Of course, the mount 290 may have otheror additional structures and/or features in other embodiments tofacilitate the securement of the inserter sensor module 104 to theacetabular prosthetic component inserter 130. In the illustrativeembodiment, the sensor module 104 is attachable to the acetabularprosthetic component inserter 130 via use of a coupler 134. Similar tothe mounting bracket 110, the coupler 134 includes a sensor mount base136, which receives the mount 290 of the inserter sensor module 104. Thecoupler 134 is securable to a handle 138 of the acetabular prostheticcomponent inserter 130. An inserter rod 140 extends from the handle 138and includes the distal end 132 to which the acetabular prostheticcomponent 160 is attached during insertion. Of course, acetabularprosthetic component inserters having different configurations may beused in other embodiments. Additionally, different mechanisms andstructures may be used to attached the inserter sensor module 104 to theacetabular prosthetic component inserter 130 in other embodiments.

Referring now to FIG. 5, each of the sensor modules 102, 104 includes asensor circuit 500. The illustrative sensor circuit 500 includes aprocessor circuit 502, a memory 504, an orientation sensor 506, adisplay 508, a communication circuit 510, and power circuitry 512. Ofcourse, each sensor module 102, 104 may include additional or othercomponents typically found in sensing components, which have not beenillustrated in FIG. 5 for clarity of the description.

The processor circuit 502 may be embodied as one or more processors andrelated components and/or circuitry. Such processors may be embodied asany type of processors capable of performing the functions describedherein. For example, the processor(s) of the processor circuit 502 maybe embodied as a single or multi-core processor(s) having one or moreprocessor cores, a digital signal processor, a microcontroller, or otherprocessor or processing/controlling circuit. Similarly, the memory 504may be embodied as any type of volatile or non-volatile memory or datastorage capable of performing the functions described herein. Inoperation, the memory 504 may store various data and/orsoftware/firmware used during operation of the sensor modules 102, 104including, for example, the temporary storage of orientation datagenerated by the orientation sensor 506. The memory 504, and othercomponents of the sensor circuit 500, may be coupled to the processorcircuit 502 and/or other components via various interconnects such as anI/O subsystem, control hubs/busses, firmware devices, communicationlinks, and/or other components and subsystems to facilitate theinput/output operations.

The orientation sensor 506 is configured to generate sensor dataindicative of the orientation in three dimensions of the sensor module102, 104. In the illustrative embodiment, the orientation sensor 506 isembodied as, or otherwise includes, a three-axis gyroscope 520 and athree-axis accelerometer 522. The three-axis gyroscope 520 may beembodied as any type of gyroscope sensor capable of measuring therotation of the corresponding sensor module 102, 104 about the threecoordinate axes. For example, the three-axis gyroscope 520 may beembodied as a single three-axis gyroscope or a collection of single axisgyroscopes. The three-axis accelerometer 522 may be embodied as any typeof accelerometer capable of measuring acceleration of the sensor module102, 104 along the three coordinate axes. Similar to the three-axisgyroscope 520, the three-axis accelerometer 522 may be embodied as asingle three-axis accelerometer or as a collection of single axisaccelerometers. The three-axis accelerometer 522 generates accelerationdata used to correct biases in the output of the three-axis gyroscope520 due to such acceleration. In the illustrative embodiment, theorientation sensor data generated by the orientation sensor 506 isrepresented as quaternion measurements. However, in other embodiments,the orientation sensor 506 may generate sensor data in other formats.

The display 508 is embodied as one or more illumination devices such as,for example, light emitting diodes, filament lights, and/or the otherdevices capable of illumination. The display 508 is positioned behindthe power buttons 230, 270 of the sensor module 102, 104 to illuminatethe power buttons 230, 270 when the sensor module 102, 104 is turned on.With regard to the inserter sensor module 104, the display 508 alsoincludes the alignment indicator 272 as discussed above.

The communication circuit 510 may be embodied as one or more devicesand/or circuitry for enabling communications between the sensor modules102, 104 and the display module 106. The communication circuit 510 maybe configured to use any suitable wireless communication protocol tocommunicate with the display module 106 including, for example, ashort-range wireless communication protocol such as Bluetooth® or otherwireless communication protocol.

The power circuitry 512 controls the activation of the sensor module102, 104. In particular, as discussed above, the power circuitry 512supplies power to other components of the sensor module 102, 104 inresponse to selection of the power button 230, 270. However, after thepower button 230, 270 has been selected to turn on the sensor module102, 104, the power circuitry 512 continues to supply such power to thecomponents regardless of additional selections of the power button 230,270. That is, the power circuitry 512 ensures that power is continuouslysupplied to the components of the sensor module 102, 104 until a powersource (not shown) of the power circuitry 512 is depleted. In this way,the power circuitry 512 ensures that the sensor modules 102, 104 aresingle-use devices that cannot be reused in multiple surgeries.

In some embodiments, the sensor circuit 500 may also include additionalsensors 514. The additional sensors 514 may include any number and typeof sensors capable of improving the accuracy of the orientation sensordata generated by the orientation sensor 506. For example, theadditional sensors 514 may include a temperature sensor in someembodiments. The sensor output of such a temperature sensor is used tofurther correct any biases of the sensor data generated by theorientation sensor 506 due to temperature. Of course, the sensor circuit500 may include additional or other sensors in other embodiments tofurther increase the accuracy of the generated orientation sensor data.

Referring now to FIG. 6, the display module 106 includes a housing 600sized to be held in the hands of an orthopaedic surgeon and used duringthe performance of an orthopaedic surgical procedure. In this way, thedisplay module 106 is configured to be mobile. The display module 106also includes a display 602 on which visual indications of theorientation of the acetabular prosthetic component 160 relative to thepatient's bony anatomy are displayed to the surgeon. For example, avisual graphic 650 showing a virtual inserter in a position relative toa virtual patient's bony anatomy that is indicative of the currentpositioning of the acetabular prosthetic component 160 relative to theactual patient's bony anatomy may be displayed on the display 602.Additionally or alternatively, the display 602 may include orientationdata 652 identifying the determined degree or amount of inclinationand/or anteversion of the acetabular prosthetic component 160 relativeto the patient's bony anatomy as discussed in more detail below.

The display module 106 illustratively includes a plurality of user inputbuttons 604, 606, 608 positioned below the display 602. The user inputbuttons 604, 606, 608 may be “soft” buttons in that their functionalitymay change depending on the particular user interface displayed on thedisplay 602. Additionally, the display module 106 includes a powerbutton 610. The power button 610 may include a power indicator 612 toprovide a visual indication as to when the display module 106 is turnedon. In the illustrative embodiment, the power button 610 is positionedbelow the row of input buttons 604, 606, 608, but the buttons 604, 606,608 may be positioned in other configurations and/or orientations inother embodiments.

As illustrated in FIG. 7, the display module 106 includes a controlcircuit 700 positioned in the housing 600. The control circuit 700includes a processor circuit 702 and a memory device 704. The processorcircuit 702 may include, or be embodied as, any type of processor andrelated circuitry configurable to perform the functions describedherein. For example, the processor(s) of the processor circuit 702 maybe embodied as a single or multi-core processor(s) having one or moreprocessor cores, a digital signal processor, a microcontroller, or otherprocessor or processing/controlling circuit. Similarly, the memorydevice 704 may be embodied as any type of volatile or non-volatilememory or data storage capable of performing the functions describedherein. In operation, the memory 704 may store various data and/orsoftware/firmware used during operation of the display module 106.

The control circuit 700 also includes an external power input circuitry706, a rechargeable power source 708 such as a rechargeable battery orthe like, and power circuitry 710. The external power input circuitry706 is configured to receive a plug of a charger such as a “wallcharger” and is communicatively coupled to the rechargeable power source708, which is communicatively coupled to the power circuitry 710. Thepower circuitry 710 is communicatively coupled to the processor circuit702 and the power button 610. The power circuitry 710 may include powercontrol, distribution, and filtering circuitry and is configured toprovide or distribute power the rechargeable power source 708 to theprocessor circuit 702 and other devices or components of the controlcircuit 700.

The control circuit 700 also includes display circuitry 712 for drivingand/or controlling the display 602. The display circuitry 712 iscommunicatively coupled to the processor circuit 702 and the display 602to control functions thereof.

As discussed above, the display module 106 is configured to receivesensor data from each of the sensor modules 102, 104. As such, thecontrol circuit 700 includes communication circuitry 720 and an antenna722. The communication circuitry 720 is communicatively coupled to theprocessor circuit 702 and to the antenna 722. The communicationcircuitry 720 may be configured to use any type of wirelesscommunication protocol, standard, or technologies to communicate withthe sensor modules 102, 104 including, but not limited to, a short rangewireless protocol such as a Bluetooth® protocol. As discussed in moredetail below, in addition to receiving the orientation sensor data fromeach of the sensor modules 102, 104, the display module 106 may also beconfigured to communicate with the inserter sensor module 104 using thecommunication circuitry 720 to activate the alignment indicator 272 inresponse to determining that the current orientation of the acetabularprosthetic component 160 is within a reference threshold alignmentrelative to the patient's bony anatomy.

The control circuit 700 also includes a universal serial bus (USB)interface 730. The USB interface 730 is communicatively coupled to theprocessor circuit 702. The USB interface 730 may be used to downloaddata, such as orientation data, from the display module 106 to anotherdevice such as a computer. Additionally, the USB interface 730 may beused to update the software or firmware of the control circuit 700.

Referring now to FIGS. 8A-8B, in use the system 100 may be used toperform a method 800 for aligning the acetabular prosthetic component160 in a patient's surgically prepared acetabulum. The method beginswith block 802 in which an orthopedic surgeon exposes the surgical site.Subsequently, in block 804 the reference sensor module 102 and theinserter sensor module 104 are initialized. For example, as shown inFIG. 9, a method 900 may be used to initialize the sensor modules 102,104. The method 900 begins with block 902 in which each of the sensormodules 102, 104 is paired with the display module 106. Any suitabletype of pairing procedure may be used to pair the sensor modules 102,104 and the display module 106 depending on, for example, the type ofcommunication protocol used to communicate between the sensor modules102, 104 and the display module 106.

In block 904, the sensor modules 102, 104 are validated. For example, inthe illustrative embodiment, each sensor module 102, 104 is configuredto transmit identification data (e.g., a serial number, a MAC address, aglobal unique identifier, etc.) to the display module 106. In response,the display module 106 displays the received identification data so thatthe orthopaedic surgeon or other healthcare provider may validate thatthe current sensor modules are being used (e.g., by comparing thedisplayed identification data to identification data labeled on thehousings 202, 204 of the sensor modules 102, 104, in associatedpackaging, etc.).

After the sensor modules 102, 104 have been validated in block 904, thesensor modules 102, 104 may be initialized to compensate for any biasoffset of the orientation sensors 506 in block 906. For example, in someembodiments, each sensor module 102, 104 may be placed in a knownstationary position relative to each other (e.g., placed stationary on aflat surface) in block 908. In the illustrative embodiment, thereference sensor module 102 and the inserter sensor module 104 arecoupled together in a stationary position using the keyed structures240, 280 to initialize the sensor modules 104, 106 in block 910. Forexample, as shown in FIGS. 12 and 13, the sensor modules 102, 104 may becoupled together by mating the keyed structure 240 of the referencesensor module 102 with the keyed structure 280 of the inserter sensormodule 104. For example, in the illustrative embodiment, the raisedplatform 242 of the reference sensor module 102 is received in thecorresponding recess 282 of the inserter sensor module 104. When socoupled, the top surface 210 of the reference sensor module 102 abutsthe top surface 250 of the inserter sensor module 104 as shown in FIG.13.

In some embodiments, the sensor modules 102, 104 may be coupled to eachother in such mated configuration for a period of time or until thedisplay module 106 indicates that the sensor modules 102, 104 have beenproperly initialized. In other embodiments, the sensor modules 102, 104are not turned on initially until the sensor modules 102, 104 arecoupled to each other. For example, block 906 may be executed prior toblocks 902, 904 of the method 900).

Referring back to the method 800 of FIGS. 8A-8B, after the sensormodules 102, 104 have been initialized in block 804, the referencesensor module 102 is secured to the patient's bony anatomy in block 806.To do so, as discussed above and shown in FIGS. 14 and 15, the referencesensor module 102 may be attached to the sensor mount base 112 of themounting bracket 110 via the mount 244 of the housing 202 of the sensormodule 102. The mounting bracket 110 may then be secured to thepatient's bony anatomy via the bone mount base 116 using the securingdevices 120. In the illustrative embodiment, as shown in FIG. 15, thereference sensor module 102 is secured to the patient's bony anatomy inthe vicinity of the orthopedic surgical procedure. For example, themounting bracket 110 may be secured near the patient's acetabulum 1500as shown in FIG. 15.

Referring back to the method 800 of FIGS. 8A-8B, after the referencesensor module 102 has been secured to the patient's bony anatomy inblock 806, the inserter sensor module 104 is registered to thecoordinate system of the patient's bony anatomy. As shown in FIG. 16,the inserter sensor module 104 includes a sensor coordinate system 1600.The orientation sensor data generated by the inserter sensor module 104is in reference to the sensor coordinate system 1600. However, as shownin FIG. 17, the patient's bony anatomy has a separate coordinate system1700, which is not aligned with the sensor coordinate system 1600. Assuch, the inserter sensor module 104 is registered to the patientcoordinate system 1700 so that the orientation sensor data generated bythe inserter sensor module 104 can be converted to the patientcoordinate system 1700 and the orientation of the acetabular prostheticcomponent 160, relative to the patient's bony anatomy, may be determinedand displayed to the orthopaedic surgeon. The coordinate systems 1600,1700 shown in FIGS. 16, 17 are illustrative coordinate systems used inthe system 100. However, it should be appreciated that other coordinatesystem (e.g., coordinate systems having different axes) may be used inother embodiments.

Referring to FIG. 10, a method 1000 for registering the inserter sensormodule 104 with the patient coordinate system is shown. The method 1000begins with block 1002 in which the inserter sensor module 104 issecured to the acetabular prosthetic component inserter 130. Asdiscussed above, the inserter sensor module 104 may be secured to theacetabular prosthetic component inserter 130 using the coupler 134. Forexample, the mount 290 of the inserter sensor module 104 may be attachedto the sensor mount base 136 of the coupler 134. The coupler 134 maysubsequently be attached to the inserter handle 138. However, asdiscussed above, other mechanisms and structures may be used to attachthe inserter sensor module 104 to the acetabular prosthetic componentinserter 130 in other embodiments.

In block 1004, the acetabular prosthetic component inserter 130 with theattached inserter sensor module 104 is aligned with the patient's spine.To do so, as shown in FIG. 18, the acetabular prosthetic componentinserter 130 may be aligned with the patient's spine by positioning theinserter 130 approximately in line with an axis defined by the patient'sspine. Once so aligned, the sensor module 104 transmits alignment sensordata (i.e., the current orientation sensor data) to the display module106 in block 1006. Subsequently, in block 1008, the acetabularprosthetic component inserter 130 with the attached inserter sensormodule 104 is aligned with the patient's anterior superior iliac spine(ASIS) axis. To do so, as shown in FIG. 19, the acetabular prostheticcomponent inserter 130 may be aligned with an anatomical axis 1800 ofthe patient defined by the patient's anterior superior iliac spinelandmarks 1802, 1804. Once so aligned, the sensor module 104 transmitsalignment sensor data (i.e., the current orientation sensor data) to thedisplay module 106 in block 1010.

In other embodiments, the inserter sensor module 104 may be registeredto the patient coordinate system using a 1-step registration process(rather than the dual alignment of blocks 1004 and 1008). To do so, analignment frame 2600 may be used as shown in FIG. 26. The alignmentframe 2600 includes a frame body 2602 having a pair of ASIS contact feet2604, 2606 configured to contact the ASIS points of the patient. In someembodiments the contact feet 2604, 2606 are movable with respect to theframe body 2602 to allow the alignment frame 2600 to be used withpatients of varying sizes. The alignment frame 2600 also includes apubic symphysis arm 2608 extending distally from the frame body 2602 andmovable with respect to the frame body 2602. The pubic symphysis arm2608 includes a contact foot 2610 configured to contact the patient'spubic symphysis. Similar to the contact feet 2604, 2606, the contactfoot 2610 may be movable, in addition to the pubic symphysis arm 2608,to accommodate patients of various sizes and improve the ease ofcoupling the alignment frame 2600 to the patient. The alignment frame2600 also includes a cradle 2612, which is configured to receive theinserter sensor module 104. As such, to register the inserter sensormodule 104 to the patient coordinate system, the alignment frame 2600may be coupled, or otherwise placed on top of, the patient such that thecontact feet 2604, 2606 rest on the patient's ASIS points and thecontact foot 2610 rests on or contacts the patient's pubic symphysis.Once so positioned, the inserter sensor module 104 may be placed in thecradle 2612 and registered to the patient coordinate system. As withblocks 1006, 1010, the inserter sensor module 104 transmits alignmentsensor data (i.e., the current orientation sensor data) to the displaymodule 106 while secured to the alignment frame 2600 to register theinserter sensor module 104 to the patient coordinate system.

Referring back to FIG. 10, after receiving the alignment sensor datafrom the inserter sensor module 104 in blocks 1006, 1010, the displaymodule 106 determines a coordinate system conversion factor in block1012. The coordinate system conversion factor is usable to convert theorientation sensor data received from the inserter sensor module 104from the sensor coordinate system 1600 to the patient coordinate system1700. The coordinate system conversion factor may be embodied as anydata usable to perform such function. For example, in the illustrativeembodiment in which the sensor modules 102, 104 generate sensor data ina quaternion format, the display module 106 may execute a method 1100such as the one shown in FIGS. 11A-11B for determining a coordinatesystem conversion factor to convert the orientation sensor data from thesensor coordinate system 1600 to the patient coordinate system 1700. Themethod 1100 begins with block 1102 in which the alignment orientationdata received in blocks 1006, 1100, which is received in quaternionformat, is converted to a rotation matrix. The quaternion format of theorientation data is generally of the form: Q=qw+i*qx+j*qy+k*qz, whereinQ defines a rotation about a vector [Qx, Qy, Qz] by an angle of2*cos⁻¹(Qw).

To convert the quaternion format to a rotation matrix, the displaymodule 106 utilizes a rotation matrix equation 2000 as shown in FIG. 20.Subsequently, in block 1104, the rotation matrix generated in block 1102is multiplied by the alignment axis of the acetabular prostheticcomponent inserter 130 (i.e., the spinal and ASIS axes of the patient).To do so, the display module 106 may utilize a spinal axis vectorequation 2100 and an ASIS vector equation 2102 as shown in FIG. 21. Thethird axis is determined in block 1106 as mutually orthogonal to thespinal and ASIS axes. The display module 106 may utilize a vectorequation 2104, shown in FIG. 21, to determine the mutually orthogonalthird axis. Subsequently, in block 1108, the display module 106 updatesthe ASIS axis vector to be mutually orthogonal to the spinal axis andthe third axis calculated in block 1106 using a vector equation 2200shown in FIG. 22. In some embodiments, if the updated ASIS axis vectoris different from the previous ASIS axis vector by a reference thresholdamount, the display module 106 may offer the orthopaedic surgeon theoption to re-register the inserter sensor module 104 to the patientcoordinate system 1700.

In block 1110, a rotation matrix to convert from the sensor coordinatesystem of the reference sensor module 102 to the patient coordinatesystem 1700 is determined. To do so, the display module 106 utilizes arotation equation 2300 as shown in FIG. 23. In block 1112, the displaymodule then converts the rotation matrix determined in block 1110 to aquaternion coordinate system conversion factor using as quaternionequation 2400 as shown in FIG. 24. Subsequently, during the performanceof the orthopaedic surgical procedure and as discussed in more detailbelow, the orientation data received from the inserter sensor module 104(Q2) may be converted, in block 1114, from the sensor coordinate system1600 to the patient coordinate system 1700 using the quaternionconversion equation 2500 shown in FIG. 25. Of course, it should beappreciated that other coordinate system conversion factors may becalculated, or otherwise determined, in other embodiments based on thetype of orientation sensors 506 and/or the orientation data generated bysuch sensors 506.

Referring back to method 800 of FIGS. 8A-8B, after the inserter sensormodule 104 has been registered with the patient coordinate system inblock 808, the orthopaedic surgeon may select the type of orthopaedicsurgery to be performed in block 810. To do so, various surgery optionsmay be displayed to the orthopedic surgeon on the display 602 of thedisplay module 106. The orthopaedic surgeon may select the appropriatesurgery type of the displayed options or otherwise provide input to thedisplay module 106 to select or define the desired surgery type orfeatures. For example, in block 812 the surgeon may select a targetedsurgical approach in which the orthopaedic surgeon selects or supplies atargeted orientation of the acetabular prosthetic component 160 relativeto the patient's bony anatomy. To do so, the orthopaedic surgeon may,for example, enter a desired inclination angle and/or a desiredanteversion angle in block 812. Alternatively, in block 814, theorthopaedic surgeon may manually position the acetabular prostheticcomponent 160 into the patient's acetabulum in the desired finalorientation using the acetabular prosthetic component inserter 130. Onceso positioned, the display module 106 may capture the orientation data(e.g., the inclination and anteversion angles) of the acetabularprosthetic component 160 while it is placed in the desired position.Such orientation data may be subsequently used as the target orientationof the acetabular prosthetic component 160 during the orthopaedicsurgery. In other embodiments, the orthopaedic surgeon may opt for acustom surgical technique in block 816 in which no target orientation ispredetermined or otherwise supplied prior to the orthopaedic surgery.Rather, the surgeon may use the orientation data displayed by thedisplay module 106 during the orthopaedic surgery as feedback inselecting the proper orientation (i.e., the proper inclination andanteversion angles).

After the surgical technique has been selected or determined in block810, the method 800 advances to block 818 in which the orthopaedicsurgeon performs the orthopaedic surgery using the system 100. Duringperformance of the orthopaedic surgery, the display module 106 receivesorientation sensor data from each of the reference sensor module 102 andthe inserter sensor module 104 in block 820. In block 822, the displaymodule 106 converts the orientation sensor data received from theinserter sensor module 104 from the sensor coordinate system 1600 to thepatient coordinate system 1700 using the coordinate system conversionfactor as discussed above in regard to method 1100. As such, theorientation of the acetabular prosthetic component 160 may be determinedrelative to the patient coordinate system 1700 based on the conversionof the orientation sensor data received from the inserter sensor module104.

In block 824, the display module 106 displays indicia of the orientationof the acetabular prosthetic component 160 relative to the patient'sbony anatomy on the display 602. As discussed above, the indicia may beembodied as a graphic 650 of a virtual inserter positioned relative to avirtual bony anatomy of the patient based on the determined orientationof the acetabular prosthetic component 160 and/or textual orientationdata 652 that provides a numerical value of the orientation, such as therelative inclination and/or anteversion angles.

In block 826, the display module 106 determines whether the determinedorientation of the acetabular prosthetic component 160 is within areference threshold of a target orientation (e.g., the targetorientation defined in block 810). If so, the method 800 advances toblock 828 in which the display module 106 communicates with the insertersensor module to activate the alignment indicator 272. As discussedabove, in some embodiments, the alignment indicator may include a firstthreshold alignment indicator 274 and a second threshold alignmentindicator 276. In such embodiments, the display module 106 determineswhich alignment indicator 272 should be illuminated based on thedetermined orientation and the target orientation of the acetabularprosthetic component 160 (i.e., which defined threshold amount issatisfied) and communicates with the inserter sensor module to activatethe corresponding alignment indicator 272. The alignment thresholdscorresponding to the first threshold alignment indicator 274 and asecond threshold alignment indicator 276 may be defined as any type ofthreshold (e.g., a percentage or raw amount) and may be determined bythe orthopaedic surgeon, the patient's anatomy, the orthopaedic surgicalprocedure, or otherwise based on other criteria. Regardless, after thealignment indicator has been activated in block 828, the method 800advances to block 830.

If, in block 826, the display module 106 instead determines that thedetermined orientation of the acetabular prosthetic component 160 isoutside of the reference threshold of the target orientation (e.g., thetarget orientation defined in block 810), or if the display module 106determines the reference threshold of the target orientation has notbeen set, the method 800 advances to block 830. In block 830, it isdetermined whether the orthopaedic surgery has been completed. If not,the method 800 loops back to block 818 in which the orthopaedic surgeoncontinues the orthopaedic surgery.

1. A system for aligning an acetabular prosthetic component in apatient's surgically prepared acetabulum, the system comprising: areference sensor module securable to the patient's bony anatomy andincluding (i) a first orientation sensor configured to generate firstsensor data indicative of the orientation of the patient's bony anatomyin three-dimensions, and (ii) a first communication circuit to transmitthe first sensor data; an inserter sensor module securable to anacetabular prosthetic component inserter, the inserter sensor moduleincluding (i) a second orientation sensor configured to generate secondsensor data indicative of the orientation of the acetabular prostheticcomponent inserter in three-dimensions, (ii) a second communicationcircuit to transmit the first sensor data, and (iii) an alignmentindicator; a display module separate from the reference sensor moduleand the inserter sensor module, the display module including (i) adisplay, (ii) a third communication circuit configured to receive thefirst sensor data and the second sensor data, and (iii) a processingcircuit to determine an orientation of an acetabular prostheticcomponent coupled to the acetabular prosthetic component inserterrelative to the patient's bony anatomy based on the first sensor dataand the second sensor data, display indicia of the determinedorientation of the acetabular prosthetic component on the display, andcommunicate with the inserter sensor module to activate the alignmentindicator in response to the determined orientation being withinthreshold amount of a reference orientation; wherein the processingcircuit of the display module is configured to determine a coordinatesystem conversion factor to convert the first sensor data from acoordinate system of the inserter sensor module to a patient coordinatesystem of the patient's bony anatomy and determine the orientation ofthe acetabular prosthetic component inserter relative to the patient'sbony anatomy using the coordinate system conversion factor.
 2. Thesystem of claim 1, wherein the first orientation sensor comprises afirst three-axis gyroscope and a first three-axis accelerometer, andwherein the second orientation sensor comprises a second three-axisgyroscope and a second three-axis accelerometer.
 3. The system of claim1, wherein each of the reference sensor module and the inserter sensormodule includes a power button selectable to turn on the correspondingsensor module, and wherein each of the reference sensor module and theinserter sensor module is incapable of being turned off by selection ofthe power button after the corresponding sensor module has been turnedon.
 4. The system of claim 1, wherein the alignment indicator comprisesa first alignment indicator and a second alignment indicator, andwherein the processing circuit of the display module is configured to(i) communicate with the inserter sensor module to activate the firstalignment indicator in response to the determined orientation beingwithin a first threshold amount of the reference orientation and (ii)communicate with the inserter sensor module to activate the secondalignment indicator in response to the determined orientation beingwithin a second threshold amount of the reference orientation that isless than the first threshold amount.
 5. The system of claim 4, whereinthe second alignment indicator is bounded by the first alignmentindicator.
 6. The system of claim 1, wherein the processing circuit ofthe display module is configured to determine an inclination angle andan anteversion angle of the acetabular prosthetic component relative tothe patient's bony anatomy and display the inclination angle and theanteversion angle on the display.
 7. The system of claim 6, wherein theprocessing circuit of the display module is configured to display agraphical representation of the acetabular prosthetic component inserteron the display in a position based on the determined inclination angleand anteversion angle.
 8. The system of claim 1, wherein referencesensor module includes a housing having a first keyed structure and theinserter sensor module includes a housing having a second keyedstructure, wherein the first keyed structure and the second keyedstructure are keyed to each other such that the reference sensor moduleand the inserter sensor module can be coupled to each other in a singleorientation in which the first keyed structure and the second keyedstructure are mated.
 9. The system of claim 8, wherein the first keyedstructure comprises a raised platform extending upwardly from a topsurface of the housing of the reference sensor module and the secondkeyed structure comprises a recess defined in a top surface of thehousing of the inserter sensor module, wherein the raised platform isreceived in the recess when the reference sensor module and the insertersensor module are coupled to each other in the single orientation. 10.The system of claim 1, further comprising an alignment frame having aframe body, a plurality of contact feet, and cradle, wherein the contactfeet are movable relative to the frame body and the cradle is sized toreceive the inserter sensor module.
 11. The system of claim 1, whereinthe coordinate system conversion factor is based on (i) the orientationof the inserter sensor module while the inserter sensor module isaligned with a spine of the patient, and (ii) the orientation of theinserter sensor module while the inserter sensor module is aligned withan anatomical axis of the patient defined by the anterior superior iliacspine points of the patient's bony anatomy.